How to use nginx simulation for blue-green deployment

Blue-green deployment

The focus of blue-green deployment lies in the following features

• 1. The blue version and the green version exist at the same time

• 2. The actual running environment is blue or green, it can only be one of them, controlled by the switch

Advantages and Disadvantages Analysis: The advantages are its speed and rollback. And the shortcomings are also obvious. Quick rollback is possible because two sets of environments exist at the same time, so the complexity and required resources will increase because there are two sets of environments.
In addition, although the speed has been improved, in the process of implementation, the control of the switch, no matter how fast the switching speed, is still unable to achieve completely seamless switching without combining other technologies.

Simulate blue-green deployment

Next, we use nginx’s upstream to simply simulate the blue-green deployment scenario. The specific scenario is as follows. The blue version is currently active. By adjusting the nginx settings, the green version is set as the currently active version.

Preparation in advance

Start two services on the two ports 7001/7002 in advance to display different information. The demonstration is convenient. I used tornado to make an image. The different parameters passed when starting the docker container are used to display the differences in services.

docker run -d -p 7001:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "hello blue/green service： v1 in 7001"
docker run -d -p 7002:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "hello blue/green service： v2 in 7002"

Execution log

[root@kong ~]# docker run -d -p 7001:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "hello blue/green service： v1 in 7001"
70c74dc8e43d5635983f7240deb63a3fc0599d5474454c3bc5197aa5c0017348
[root@kong ~]# docker run -d -p 7002:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "hello blue/green service： v2 in 7002"
6c5c2ea322d4ac17b90feefb96e3194ec8adecedaa4c944419316a2e4bf07117
[root@kong ~]# curl http://192.168.163.117:7001
hello, service :hello blue/green service： v1 in 7001
[root@kong ~]# curl http://192.168.163.117:7002
hello, service :hello blue/green service： v2 in 7002
[root@kong ~]#

Start nginx

[root@kong ~]# docker run -p 9080:80 --name nginx-blue-green -d nginx
d3b7098c44890c15918dc47616b67e5e0eb0da7a443eac266dbf26d55049216a
[root@kong ~]# docker ps |grep nginx-blue-green
d3b7098c4489    nginx           "nginx -g 'daemon ..."  10 seconds ago    up 9 seconds    0.0.0.0:9080->80/tcp   nginx-blue-green
[root@kong ~]#

nginx code segment

Prepare the following nginx code snippet and add it to /etc/nginx/conf.d/default.conf of nginx. The simulation method is very simple. Use down to indicate that the traffic is zero (weight cannot be set to zero in nginx). At the beginning, 100% of the traffic was sent to the blue version.

http {
upstream nginx_blug_green {
  server 192.168.163.117:7001 weight=100;
  server 192.168.163.117:7002 down;
}
server {
  listen    80;
  server_name www.liumiao.cn 192.168.163.117;
  location / {
    proxy_pass http://nginx_blug_green;
  }
}

How to modify default.conf

You can achieve the effect by installing vim in the container, you can also modify it locally and pass it in through docker cp, or directly sed Modifications are possible. If you install vim in a container, use the following method

[root@kong ~]# docker exec -it nginx-lb sh
# apt-get update
...省略
# apt-get install vim
...省略

Before modification

# cat default.conf
server {
  listen    80;
  server_name localhost;
  #charset koi8-r;
  #access_log /var/log/nginx/host.access.log main;
  location / {
    root  /usr/share/nginx/html;
    index index.html index.htm;
  }
  #error_page 404       /404.html;
  # redirect server error pages to the static page /50x.html
  #
  error_page  500 502 503 504 /50x.html;
  location = /50x.html {
    root  /usr/share/nginx/html;
  }
  # proxy the php scripts to apache listening on 127.0.0.1:80
  #
  #location ~ \.php$ {
  #  proxy_pass  http://127.0.0.1;
  #}
  # pass the php scripts to fastcgi server listening on 127.0.0.1:9000
  #
  #location ~ \.php$ {
  #  root      html;
  #  fastcgi_pass  127.0.0.1:9000;
  #  fastcgi_index index.php;
  #  fastcgi_param script_filename /scripts$fastcgi_script_name;
  #  include    fastcgi_params;
  #}
  # deny access to .htaccess files, if apache's document root
  # concurs with nginx's one
  #
  #location ~ /\.ht {
  #  deny all;
  #}
}
#

After modification

# cat default.conf
upstream nginx_blug_green {
  server 192.168.163.117:7001 weight=100;
  server 192.168.163.117:7002 down;
}
server {
  listen    80;
  server_name www.liumiao.cn 192.168.163.117;
  #charset koi8-r;
  #access_log /var/log/nginx/host.access.log main;
  location / {
    #root  /usr/share/nginx/html;
    #index index.html index.htm;
    proxy_pass http://nginx_blug_green;
  }
  #error_page 404       /404.html;
  # redirect server error pages to the static page /50x.html
  #
  error_page  500 502 503 504 /50x.html;
  location = /50x.html {
    root  /usr/share/nginx/html;
  }
  # proxy the php scripts to apache listening on 127.0.0.1:80
  #
  #location ~ \.php$ {
  #  proxy_pass  http://127.0.0.1;
  #}
  # pass the php scripts to fastcgi server listening on 127.0.0.1:9000
  #
  #location ~ \.php$ {
  #  root      html;
  #  fastcgi_pass  127.0.0.1:9000;
  #  fastcgi_index index.php;
  #  fastcgi_param script_filename /scripts$fastcgi_script_name;
  #  include    fastcgi_params;
  #}
  # deny access to .htaccess files, if apache's document root
  # concurs with nginx's one
  #
  #location ~ /\.ht {
  #  deny all;
  #}
}
#

Reload nginx settings

# nginx -s reload
2018/05/28 04:39:47 [notice] 321#321: signal process started
#

Confirm the result

The output of all 10 calls is v1 in 7001

[root@kong ~]# cnt=0; while [ $cnt -lt 10 ]
> do
> curl
> let cnt
> done
hello, service :hello blue/green service： v1 in 7001
hello, service :hello blue/green service： v1 in 7001
hello, service :hello blue/green service： v1 in 7001
hello, service : hello blue/green service： v1 in 7001
hello, service :hello blue/green service： v1 in 7001
hello, service :hello blue/green service： v1 in 7001
hello, service :hello blue /green service： v1 in 7001
hello, service :hello blue/green service： v1 in 7001
hello, service :hello blue/green service： v1 in 7001
hello, service :hello blue/green service: v1 in 7001
[root@kong ~]

#Blue-green deployment: switch to the green version

By adjusting default.conf weight, and then execute nginx -s reload. You can dynamically switch to the green version without stopping the nginx service. The target will output all traffic to v2 in 7002

Modify default .conf method

You only need to adjust the weight of the server in upstream as follows:

upstream nginx_blug_green {
  server 192.168.163.117:7001 down;
  server 192.168.163.117:7002 weight=100;
}

Reload nginx settings

# nginx -s reload
2018/05/28 05:01:28 [notice] 330#330: signal process started
#

Confirm the result

[root@kong ~]# cnt=0; while [ $cnt -lt 10 ]; do curl ; let cnt ; done
hello, service :hello blue/green service： v2 in 7002
hello, service :hello blue/green service： v2 in 7002
hello, service :hello blue/green service： v2 in 7002
hello, service : hello blue/green service： v2 in 7002
hello, service :hello blue/green service： v2 in 7002
hello, service :hello blue/green service： v2 in 7002
hello, service :hello blue /green service： v2 in 7002
hello, service :hello blue/green service： v2 in 7002
hello, service :hello blue/green service： v2 in 7002
hello, service :hello blue/green service: v2 in 7002
[root@kong ~]

#

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